Artificial Sweeteners When Trying to Conceive or Become Pregnant: Bad Idea?

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n part 5 of my Foods for Fertility series, we talked about how when it comes carbs, it’s a good idea to stick to whole grains and avoid sugar as much as possible! And the number 1 way of avoiding simple carbs is to stop drinking sugary soda.

But you know what, for a lot of us that’s easier said than done. Why does sugar taste so great again? Sucks that our brain just LOVES those dopamine induced sugar-highs! So what’s a girl to do? Stop eating and drinking any and all sweets? There’s got to be a better way, right?

So in part 6 of my Foods for Fertility series, we talk about artificial sweeteners when TTC’ing. Are they safe? Do they reduce fertility? Let’s find out.

Part 1. The Ultimate Fertility Diet: What To Eat When Trying to Conceive
Part 2. Meat, Poultry, Fish, Tofu: Which Protein is Best and Which is Worst for Fertility?
Part 3. Definitive Guide to Fats That HELP Fertility: Omega-3 and Other Fatty Acids
Part 4. Definitive Guide to Fats That HURT Fertility: Saturated Fats and Other Fats
Part 5. Sugar and Other Carbs Suck When Trying to Conceive
Part 6. Artificial Sweeteners When Trying to Conceive or Pregnant: Bad Idea?
Part 7. Two Reasons Coffee is Bad When Trying For a Baby
Part 8. Can I Drink Alcohol When Trying to get Pregnant?
Part 9. Dairy Can Help You Get Pregnant – Everything You Need to Know
Part 10. 10 Fertility Diet Tips to Implement Today


Note: I interpret scientific studies but my interpretation is not medical advice.

The quick win

Wait! Before you continue reading, consider doing ONE easy thing that is known to boost fertility: taking a daily high-quality prenatal multivitamin. This is without doubt the easiest way to boost your fertility (here’s why). Personally, I love the Smartypants prenatal gummy (because it’s good and tastes yummy) and the Nature Made prenatal vitamin with DHA (because it contains all kinds of goodies that boost fertility and is a trusted brand). (affiliate links).

Ditch sugar for artificial sweeteners?

ditch sugars for artificial sweeteners?

As the most commonly used sweetener, sugar is a simple carbohydrate that’s (by definition) very high on the glycemic index. And as I’ve discussed before, you should really try to limit high glycemic, sugary foods when trying to get pregnant. This also includes things like high fructose corn syrup, maple syrup and honey! But… we are all human. And humans like sweet stuff, it’s as simple as that. I’m not saying you should completely avoid sugar, but making an effort to limit it is a good idea.

But what about low calorie natural and artificial sweeteners? Do they influence fertility in any way? And are they even safe to use when you’re trying to conceive and after you’ve gotten pregnant?

foods for fertility free ebook

A lot has been said and written about artificial sweeteners in the context of general health, but not that much is known about sweeteners and fertility. I know a lot of women are against the very idea of artificial sweeteners. And I get that. It doesn’t sound great to put anything “artificial” in your body, especially when you could soon have a little person growing in your belly.

But before deciding if you should leave that Diet Coke behind and stick to just water, let’s go over the evidence so that you can make an informed decision.

Artificial sweeteners, fertility and pregnancy

After sugar, the most common (artificial) sweeteners in the United States are saccharin (Sweet ‘N Low), aspartame (Nutrasweet or Equal), sucralose (Splenda), Stevia, acesulfame potassium (Ace-K, Sweet One), and cyclamate. All of these are FDA-approved and considered safe in low amounts, especially considering these are so much sweeter than sugar, so you only consume a very small amount in each serving. There is an exception though but I’m still including it in this article: cyclamate. It is not FDA approved, but it is a very popular sweetener outside the US.

So let’s dive deep into what the science says on how sweeteners relate to fertility. And of course, I’ll also go over whether using sweeteners is a good idea while pregnant, because you want to make absolutely sure they’re not a problem in pregnancy either.

Saccharin (Sweet ‘N Low) & Fertility

Saccharin and fertility

Saccharin is an artificial sweetener that’s more than 300 times sweeter than sugar and it’s used in many different foods. But perhaps is it best known as the “pink” sweetener, or Sweet ‘N Low, as you would see on tables at diners across the country.

Let’s talk about a recent study which set out to investigate whether saccharine could influence the female estrous cycle, and if so, how it would do that.1 The researchers gave female rats a daily dose of saccharin for 48 straight days and observed whether there was any influence -good or bad- to the reproductive system.

They found that the hormonal feedback from sex hormones was in fact changed in rats who ingested lots of saccharin. Specifically, saccharin treated rats had longer estrous cycles, higher levels of the reproductive hormone progesterone, and an increased number of ovarian cysts. The rats even showed weight gain as well!

Now… maybe you’ve figured it out by now, all of these signs and symptoms sound a lot like PCOS, Polycystic Ovary Syndrome. Weight issues, ovarian cysts and disrupted cycles. And this is exactly what the researchers say as well!

You should keep in mind that the FDA has set a daily acceptable intake limit of 15 milligrams of saccharin per kilogram of body weight, while the rats in this study received MUCH higher doses many days in a row, 10 to 50 times as much saccharin to be exact. So odds are, you’ll be fine, but it probably pays to keep an eye on any products that might contain saccharin, and limit the amount you ingest.

Saccharin (Sweet ‘N Low) & Pregnancy

There’s another reason why you might want to cut out saccharin from your diet, and that is, once you get pregnant -and that is of course the end goal here- it can easily cross into the fetal bloodstream through the placenta.2,3 Once it’s there, it takes a really long time for saccharin to be excreted away from the fetus than it does from your own body.3 And that doesn’t sound all that great.

Now, in another study mice were exposed to very high doses of saccharin (hundreds of times higher than the acceptable daily intake for humans), and there were no malformations to  the fetus.4 And in yet another study where women who consumed saccharin were compared to women who didn’t consume saccharin, there was no difference in the number of spontaneous abortions. In other words, moderate saccharin doesn’t seem to be associated with miscarriages.

Looking beyond saccharin use and conception, there is a lot of controversy surrounding this substance, most importantly, it one point it was said that saccharin use could cause bladder cancer. The American Cancer Institute says that this finding was only shown in one study using rats but that all subsequent studies could not find any link between saccharin and cancer in humans, even after very extensive research.5

So yes, overall, saccharin is safe in doses that we would typically consume, but the fact that it can influence reproductive hormones and, once you get pregnant, it can easily reach the developing fetus should be enough of a reason to avoid saccharin.

Aspartame (Equal) & Fertility

aspartame and fertility

Aspartame -also known as NutraSweet or Equal- might be the most widely used artificial sweetener of all, and it’s probably one of the most controversial too.

It’s used in sugar-free soda, cookies, fruit juices, chewing gum and many other things. And let me tell you, a LOT has been written about aspartame and how bad it (supposedly) is, but the general scientific consensus is actually that it is safe to consume in small quantities.6

For example, an average adult would have to drink more than three 2-liter bottles of diet coke in a single day in order to exceed the FDA limit. In any case, I will focus on potential fertility effects of aspartame.

But when it comes to fertility, there is a surprisingly small body of research on aspartame.

In one of the very few studies conducted recently, obese female rats were given a dose of 5 to 7 milligrams of aspartame per kilogram of body weight, which is about equivalent to 2 cans of diet soda. And researchers found no obvious negative effects on the ability of the rats to get pregnant.6,7

Aspartame (Equal) & Pregnancy

Aspartame is also considered safe to consume during pregnancy, at least in amounts up to several times the FDA daily limit.

The biggest reason it’s considered safe is a rather interesting one, it’s because aspartame does not enter your bloodstream.8

Aspartame is already broken down in the gut into three components: aspartic acid, Phenylketonuria (PKU), and methanol. With the exception of PKU which is only dangerous if you have a very rare metabolic disorder, these components are not dangerous in moderate amounts.

These individual components can cross the placenta though, but in the small quantities you would typically consume aspartame they are not considered dangerous to the fetus.9

So because aspartame is broken down in the intestine, it will not enter the bloodstream, and it will not be transmitted to the fetus or even breast milk.10

So what’s the deal with aspartame? You probably keep hearing bad things about it. And yes, some studies have indeed been less than positive about aspartame.

For example, it has been said that aspartame can even damage or alter DNA! And while that doesn’t sound all that great, you shouldn’t be worried.

What’s happening is that these studies are done “in vitro” which means they are tested outside of the body, basically, in a test tube. And since aspartame does not enter your bloodstream, and can therefore not interact with other tissues including a fetus, making those horror stories more or less irrelevant.

In huge studies with thousands of participants where aspartame is tested as an actual food you eat, no associations are found with DNA damage or cancer or anything like that, including in pregnant women. 8,11,12,13

The research suggests that as long as you stay well below the FDA-approved acceptable daily intake level, it should be fine. But of course, I’m not an expert on aspartame, so I invite you to do your own research, starting with information from the Food and Drug Administration.

Sucralose (Splenda) & Fertility

sucralose and fertility

Sucralose, better known as Splenda, is a popular artificial sweetener that is actually made from sugar but is modified chemically to become much sweeter and much lower in calories.

While there are no studies in women on sucralose and fertility, we do have evidence from animal studies.

For example, when rats are fed sucralose to the tune of 100 times or more the expected daily human intake there is no change in any fertility metrics.14 This includes no changes to estrous cycles and mating behavior.

In other words, researchers from this study couldn’t find any negative fertility consequences of giving female rats high doses of sucralose. And the authors also note that when it comes to sucralose, the vast majority is not even absorbed and metabolized by your body. To put it bluntly: you simply poop most of it out!

And another study found that in sucralose-treated rats the mating performance and fertility were similar compared to rats who did not receive sucralose.15 Now, I don’t know how the researchers determined rat mating performance, but all I need to know is that their “performance” was the same!

Sucralose (Splenda) & Pregnancy

When it comes to pregnancy, the same study in rats that we just discussed also looked for fetal and pregnancy related changes due to sucralose intake.14

The scientists found no negative effects of Splenda on gestation, maternal and fetal viability, fetal development, giving birth, pup maturation or lactation. Mind you, these rats were exposed to very high doses of Splenda, higher than humans would under any normal circumstances!

Stevia & Fertility

Stevia and fertility

Stevia is quickly becoming a popular alternative to artificial sweeteners. It is a natural low-calorie sweetener derived from a Stevia rebaudiana plant which is native to Brazil.

I know “Natural” sure sounds a lot better than “artificial”, but does it affect fertility?

Well… One small, but well designed study investigated whether stevia had any negative effects on the ability of obese rats to reproduce.7 And in this same study, the researchers also looked at aspartame and fertility.

Just like we know discussed a few paragraphs back, aspartame consumption did not have a negative effect on conception. But Stevia on the other hand… Stevia did not fare that well.

Mind you, the researchers made sure to give stevia in moderate amounts to the rats, amounts well within the acceptable range of human consumption. To be exact, rats were given an oral dose of 2 to 3 milligram per kilogram of body weight per day.

To put this in perspective, the FDA allows for the consumption of up to 4 milligrams per kilogram of body weight per day in humans. So about the same.

A single can of Zevia, a drink sweetened with Stevia, contains 158 milligrams of Stevia.16 For a woman weighing 165 pounds, or 75 kilograms that’s about 2 milligrams per kilogram of body weight. In other words, the rats in this study were given the same amount of Stevia that a you or I could easily consume in a single day; one can of Stevia-sweetened soda.

Stevia & Fertility – a contraceptive?

So how did the rats actually fare when it came to fertility? First, in this study, non-obese rats who were not fed stevia had a 100% conception rate (wish it was that easy with us humans!). And obese rats and obese rats who were fed aspartame had an 80% chance of conceiving.

But Stevia-fed obese rats only had a 53% chance of conceiving.7 Not 100%, not 80%, but 53%! You could almost argue Stevia has contraceptive effects!

A much older study from the 1960’s showed very similar results. Scientists here showed that Stevia fed mice had a lot of difficulty conceiving,17 with the conception rate being cut in half. But in this study, the rats were fed a LOT of Stevia, way more than any human would typically consume.

Enough with the bad news: there are several other animal studies which did not find any contraceptive or anti-fertility effects of Stevia.18

But, considering I know that you are doing everything you can to optimize your fertility, you should probably stay clear of Stevia for the time being!

Stevia & Pregnancy

If for some reason you can’t cut out Stevia completely, it’s good to know that it isn’t harmful during pregnancy.

In the rat study we just discussed, the rats that did end up pregnant had a 100% birth rate.7 However, there is no data on Stevia use during human pregnancies, so all I can say is: we don’t know.

Acesulfame Potassium (Ace-K, Sweet One) & Fertility

Ace-k and fertility

Acesulfame potassium has the dubious distinction of perhaps having the least catchy name of all sweeteners. So let’s use the much easier Ace-K acronym!

Ace-K is used in a lot of foods. It’s a popular sweetener in diet and no calorie sodas, baked goods, ice cream and even toothpaste. But, not much research has been done on Ace-K and fertility.

One particularly interesting study from 1980, describes how both male and female rats were given varying doses of Ace-K across several generations for 12-weeks prior to mating, as well as during pregnancy.

Rats were fed 1% or 3% acesulfame potassium in their diet. That is a lot of sweetener.19 Can you imaging eating more than an ounce (36 grams) of pure super-sweet artificial sweetener?

Well, the researchers found that there was no change in the number of young per litter, birth weight and mortality, and that growth rate was slightly reduced in the double dosage group.

Acesulfame Potassium (Ace-K, Sweet One) & Pregnancy

Just like with fertility, there’s not a lot of research out there on Ace-K consumption during pregnancy. One mouse study showed that prenatal and postnatal exposure of Ace-K through amniotic fluid and breast milk resulted in offspring having a preference for sweet foods once they reached adulthood.20

In a study where women were asked to consume a diet soda drink containing Ace-K and sucralose (Splenda),21 both substances were found in breast milk 2 to 5 hours after consumption. Exactly what effects this could potentially have is not very well known.

But it has been suggested that the higher levels of Ace-K and sucralose could increase a preference for sweet taste, weight gain and glucose intolerance.

There is a bit of evidence that Ace-K can be transferred to the fetus and that this could also be related to a preference of sweeter foods.  But that’s all pretty speculative.

In other words, Ace-K is not dangerous so long as you stay well below the FDA approved daily intake limits. But in the name of optimizing your fertility and health to the fullest, it certainly wouldn’t hurt to limit the consumption of Ace-K.

Cyclamate & Fertility

cyclamate and fertility

Cyclamate, also called sodium cyclamate, is an artificial sweetener that is 30 or so times sweeter than sugar. That’s much less sweet than for example Saccharin or Aspartame. And this is a sweetener that is NOT approved by the FDA, so consumers in the United States should not encounter this substance anywhere.

Once upon a time, it was approved for consumption by the FDA in the 1950’s, only to be completely banned in 1970.22 It was thought that Cyclamate is carcinogenic, that it could lead to cancer. This was based on an animal study where a small percentage of rats developed bladder cancer after being fed cyclamate in doses so high, it would be the equivalent of a human consuming 550 cans of diet soda.23 Since then, all new scientific evidence points to cyclamate not being related to cancer,24 but the FDA ban still stands to this day.

So why discuss this sweetener at all if you can’t buy it? Well, I know that many of you are not from the United States, but from Europe, Australia or Asia, and cyclamates are perfectly legal over there and it’s used in food, drinks or as a tabletop sweetener all over the world.25

So does cyclamate influence fertility?

One study conducted back in 1975 found that adding 1% cyclamate to the diets of both male and female mice did not alter the mice’s ability to conceive and did not cause an increase of miscarriage.26 And 1% of your diet consisting of cyclamate is an unrealistically high dose. And while some studies show that very high doses of cyclamate can cause fertility issues in male rats, a human study from 2003 found absolutely no link between cyclamate use and male fertility.27

Cyclamate & Pregnancy

Research on cyclamate safety in pregnancy goes back many years. In a well designed study from 1968,28 researchers provided high daily doses of cyclamate to rats (and some other rats were given Saccharin) while they were pregnant. In the end, litter size and fetal weight were the same for cyclamate fed rats and rats who were fed a regular diet. They also did not find any fetal malformations. The researchers conclude that even when feeding rats cyclamate to the tune of 250 milligrams per kilogram of bodyweight it did not have any negative effects on the developing fetus.

To put that in perspective, that dose of cyclamate given to rats every day, would be about as sweet as a whole pound of sugar. Every day. The European Union has set the cyclamate Acceptable Daily Intake at 17 milligrams per kilogram of bodyweight.29

A more recent study from 2006 showed that injecting cyclamate into pregnant rats (I know, that sounds pretty terrible, why not just put it in their food!) was associated with lower weight fetuses and placentas.30 The authors note that cyclamate can pass through the placental barrier and reach and accumulate in the fetus.3,30,31

So as with saccharin, cyclamate can cross the placenta, although the effects on the developing fetus aren’t known. Because of that, it’s probably best to avoid consuming cyclamate sweeteners, even when you’re just trying to conceive but aren’t pregnant yet.

And if you’re in the United States, you have nothing to worry about since it’s complete banned anyway!

Which to avoid and which are OK

Alright, you made it till the end of this article! I know it’s a lot of info to digest, so let’s summarize what the science says about each of these artificial sweeteners relate to fertility and pregnancy.

Saccharin: limit or avoid

When it comes to saccharin, it’s a good idea to avoid it because (1) there might be a link with disrupted cycles and hormone disturbances and (2), it crosses the placenta.

Aspartame: OK in moderation

Limited research suggests the aspartame does not influence fertility, similarly, animal studies do not raise any concerns with the use of aspartame during pregnancy.

Sucralose: OK in moderation

Studies suggest there is no negative effect on fertility or on the fetus during pregnancy.

Stevia: limit or avoid

Animal studies suggest there may be a link with reduced fertility when consuming Stevia although the jury is still out. Stevia consumption during pregnancy should be considered safe, although there are no data of human studies.

Ace-K: limit or avoid

Fertility is probably not affected, but the substance can cross placental barrier into the fetus and even breastmilk. There’s little hard evidence of negative effects, except perhaps that offspring could like sweeter foods more.

Cyclamate: limit or avoid

Banned in the US but not elsewhere in the world. It is unlikely to affect fertility. There is also no indication there are any negative effects to the fetus during pregnancy, but the substance does cross the placenta, so it’s probably best to limit or avoid it.

Final thoughts

ditch sugars and artificial sweeteners when trying for a baby?

Before you throw out all foods with any artificial sweeteners let me say that these sweeteners are approved by government agencies for human consumption, and that also means during pregnancy.

The purpose of this article is not to tell you what to do. I’m not in the position to give advice. But if you want to optimize your fertility to the fullest and do everything you possibly can to get your body ready for pregnancy, maybe it’s time to take a hard look at what’s in your pantry.

And if you don’t want to completely cut out sweeteners from your life, that’s fine too, just make sure you stay below the FDA Acceptable Daily Intake limits, which shouldn’t be that hard since the limits is set rather high.


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